Psoas major is a polyarticular muscle, which runs inside body from lower back bone to its forward inward downward direction, front inner thigh bone, by crossing over pelvis. On its way, Psoas major combinds with Iliacus to form Iliopsoas.
Actions of Psoas major are flexion and external rotation of the hip joint.
Since it is an inner muscle, it is very hard to be aware its working. However, it starts functioning in the early stage of human life because when a baby starst to sit up or crawls it is already awakened.
Iliopsoas (Psoas major together with iliacus) is used constantly when we stand, walk or run in regular basis. But if it is not used for a long time, it will get shorten and contracted because it is a typical posture muscle and made with slow twitch fibers. That’s why those old people who have a sedentary life style have lower back pain.
With almost all asanas you can strengthen or stretch this muscle.
- Utthita Hasta Padangusthasana D (strengthen by flexion and lateral rotation of the leg)
- Virabhadrasana 2 (strengthen by flexing the upper body, forward tilting the pelvis, straightening and supporting the lower back)
- Ustrasana (stretches by extension of the upper body and contracting hip muscles together with contraction of quadriceps)
l Gluteus maximus
l Tensor fascia lata
l Rectus femoris
As part of the iliopsoas, psoas major contributes to flexion and external rotation in the hip joint. On the lumbar spine, unilateral contraction bends the trunk laterally, while bilateral contraction raises the trunk from its supine position.
It forms part of a group of muscles called the hip flexors, whose action is primarily to lift the upper leg towards the body when the body is fixed or to pull the body towards the leg when the leg is fixed or to pull nothing when both legs and body are fixed..
For example, when doing a situp that brings the torso (including the lower back) away from the ground and towards the front of the leg, the hip flexors (including the iliopsoas) will flex the spine upon the pelvis.
Due to the frontal attachment on the vertebrae, rotation of the spine will stretch the psoas.
Tightness of the psoas can result in lower back pain by compressing the lumbar discs